This invention relates to an overfill protecting arrangement for a liquid storage tank.
A particularly important field of use of the invention is for oil tankers, and more particularly for oil barges, and in the following the invention will be described with reference to this field of use, though it is to be understood that the invention is equally applicable to other uses where similar problems exist.
For the economic utilization of oil cargo vessels it is essential that it should be possible to load their tank or tanks up to almost 100% of their volumetric capacity without incurring any risk of rupture, explosion or environmental calamities.
In vessels equipped with high level electronic control systems it is well known to provide a liquid level sensor in the tank serving to deliver a feed-back signal to the loading pump to reduce the loading rate when the liquid level is approaching the top level of the tank, and to interrupt loading entirely, when a predetermined filling degree, say 97%, has been reached.
However, a need also exists for an overfill protecting arrangement not depending on the presence of an electronic control system communicating with a loading pump at a loading station.
Overfill protecting systems have been proposed, which comprise a spill valve acting in conjunction with a venting valve of the tank. In systems of this type, when the liquid level reaches the top level of the tank, the spill valve is opened by the tank pressure, and overflow commences. As soon as this is observed by a person aboard the vessel in charge of surveying loading, he shall issue a command to the loading station operator to stop loading.